The presence of endemic infectious viruses is a serious complication of research involving laboratory rodents. Present viral detection systems rely largely on detecting antibody responses in serum assays. Although these systems have markedly improved in sensitivity during the past ten years, they are inadequate to test for pathogens or extraneous viruses in immunodeficient rodents or recently infected animals. This application seek to adapt an existing new technology, polymerase chain reaction (PCR), for the detection of selected viruses relevant to the laboratory animal field. The specific aims of this application are: I. To develop a sensitive system for detecting murine viral pathogens by using DNA amplification via the polymerase chain reaction (PCR) technique. Rotavirus will be used as a prototype system to evaluate feasibility and to optimize assay conditions. a) Develop a basic PCR protocol for the detection of rotavirus in vitro and compare its sensitivity to culture and solid-phase antigen detection systems. b) Examine the additional sensitivity gained by the use of: 1) nested pairs of primers, and 2) an immunocapture step to concentrate and partially purify the viral particles. II. To test the in vivo sensitivity and specificity of the above method. a) Measure the detection threshold of this PCR protocol for virus present in mouse bedding material. b) Compare this protocol with current serological and antigen detection methods, in acutely infected immune-competent and Severe Combined Immune Deficient (SCID) mice. III. Finally, to adapt the optimal methods identified in I and II above to the detection of murine coronavirus, a major problem in mouse colonies worldwide.